1. Field of the Invention:
This invention is directed to a vaccine for Potomac Horse Fever, effective in the prevention of occurrence of the disease in horses and related mammalian species. A method of preparing and administering the vaccine is also addressed.
2. Identification of the Disease and its Agent
In summer of 1979 a new equine disease was documented in this country, first appearing in Montgomery County, Md. In subsequent years, outbreaks of the disease, appearing in contagionfashion in certain instances, appeared from coast to coast, and in Canada. Although the symptoms of the disease are diverse, and associated with a large variety of equine diseases, repeated outbreaks under similar conditions, yielding similar results suggested a single causitive agent responsible for the new disease.
The agent was finally identified and named in 1985, Holland et al, 227 Science, pages 522-524 (1985). In the Ehrlichia family, the agent has come to be designated Ehrlichia risticii, or E. potomacensis. Shortly thereafter, the identity of the agent was confirmed, and a relatively quick enzyme-linked immunosorbent assay (ELISA) to determine the presence of the agent which generates symptoms similar to many other diseases, was developed. Dutta et al, 22 Journal of Clinical Microbiology 2, pages 265-269 (1985).